NDCMP Weather Forecast

Forecaster: Ben Schaefer

Synopsis

Strong to severe thunderstorms are possible across both districts late this afternoon through the overnight hours. An upper-level shortwave trough will move across eastern MT and western ND this afternoon and evening, helping to break down the ridge that has been sitting over western ND over the past few days and will provide the focus for active weather across the region. At the surface, a low pressure is forecasted to deepen over northeastern WY and southeastern MT, with an accompanying dry-line draped to its south, and a quasi-stationary/warm front oriented south-to-north across eastern MT. This surface low and front will likely provide initiation for storms that will effect both districts this evening.

This morning, the surface low, although relatively weak (~1010 mb), is already generating moist, warm air advection across the region. 60s dew points are already being recorded across western ND. Throughout the afternoon, the surface low and stationary front will provide enhanced moisture pooling concentrated over eastern MT and extreme western ND. Here, dew points could reach the upper 60s and maybe even low 70s, yielding MLCAPE values in access of 2000 J/kg. Further east away from the low, particuarly in eastern district 2, the surface is expected to dry out a bit, with relatively lower dew points in the upper-50s, and MLCAPE values <1000 J/kg.

Some variability exits in the severe weather threat across district 2. This is driven by the surface moisture gradient that will likely be in place. The highest threat for severe hail will exist in the western 1/3 of D2, perhaps out near Williston and Watford City, and westward. Here, supportive thermodynamics, including mid-level lapse rates in access of 8C/km are possible. Now, 0-6km shear will be on the mild side across the entire district; 20-30kts. Storms will strengthen in eastern MT during the midafternoon hours, and gradually move east into or near D2 this evening. The environment in western D2 will be supportive of multicell thunderstorms, perhaps an embedded supercell or two with severe hail if shear is on the order of 30 kts. As the storms move east, expect them to grow more linear, with perhaps a squall line and damage winds being possible. However, as the storms move into eastern D2, they will encounter more CIN and less CAPE, meaning they will likely weaken and become more elevated, certainly less ideal for seeding. Expect these storms to exit shortly after sunset. Overnight, western ND will remain in southeastern flow given a slow-moving synoptic system. A low-level jet will develop overnight, and with adequate moisture, could be supportive of pop-up, elevated thunderstorms with brief hail threats. This will likely last until sunrise, when no significant weather expected until the end of the period.

Now, District 1 will likely have a relatively higher chance to see organized, severe convection. Being closer to the surface low, dew points will likely be well into the 60s, with CAPE in access of 1000 J/kg, and maybe even 2000 J/kg across western Bowman County. Along with supportive thermodynamics and forcing, 0-6km shear values could range from 30-45kts across the district this evening. This kind of environment will be favorable for organized severe thunderstorms, with perhaps an embedded supercell or two, capable of producing severe hail and winds. These storms will likely intensify across eastern MT during the mi-afternoon and slowly make their way towards district this evening, weakening gradually as they move east and exiting district shortly after sunset. Like D2, isolated elevated storms are possible overnight with a strengthening low-level jet, with the threat ending around sunrise.

8/19/24

Indices

Weather Features

• Dir Wind Shear
• Dry Line/Slot
• Low Level Jet
• Low-Level Moisture Advection (SE)
• Short Wave Trough
• Speed Shear
• Surface Low
• Surface Trough
• Warm Front

Soundings